Arylhydrazinopyrimidines inhibit the replication of DNA in gram-positive bacteria. Evidence from our laboratory suggests that these inhibitors act at the molecular level as analogs of 2'-deoxyribonucleoside-5'-triphosphates. They are, consequently, novel tools for dissecting the enzymatic mechanism of DNA replication. The objective of this proposal is to determine the physical and chemical factors which lead to competitive inhibition of bacterial DNA synthesis by 6-(p-hydroxyphenylhydrazino) uracil and 6-p-hydroxyphenylhydrazino) isocytosine. We will study: 1) the Watson-Crick type pairing of these inhibitors with the deoxyribonucleosides (deoxycytidine and thymidine, respectively) whose complementary bases they mimic; 2) the pairing of inhibitors with appropriate oligodeoxynucleotides; 3) binding of inhibitors to specific DNA polymerase (DNA polymerase B of B. subtilis) which they inhibit, and; 4) effects of the presence of both enzyme and template DNA on the pairing and binding equilibria described above. These phenomena will be studied primarily by nuclear magnetic resonance spectroscopy. We will also determine: 1) crystal structures of the inhibitors by single-crystal X-ray diffraction; 2) crystal structures of proposed inhibitor: deoxyribonucleoside hydrogen-bonded complexes, and 3) all-valence electronic structures of the inhibitors considered as deoxyribonucleoside analogs.